CN101738601B - System and method for measuring speed of locomotive based on radar near field echo power spectrum characteristics - Google Patents

Abstract

The invention discloses a locomotive speed measurement system and method based on radar near-field echo power spectrum characteristics, and mainly solves the problems of large error and instability in locomotive speed measurement in the prior art. The measurement system of the present invention includes a sampling rate selection module, a frequency spectrum center of gravity method estimation speed module, a speed correction module and an antenna beam angle error resistance module. Select the sampling rate module to select the sampling rate corresponding to the current speed to ensure that the relative error of the measurement speed in the subsequent modules meets the speed measurement accuracy requirements. The spectral center of gravity estimation speed module pre-estimates the speed of the locomotive, and the pre-estimated locomotive speed is corrected by speed The module and the anti-antenna beam angle error module perform primary and secondary corrections to obtain the final estimation result of the locomotive speed. The invention has the advantages of small calculation amount, good stability and high speed measurement precision, and can be used for accurate measurement of the speed of the locomotive by the locomotive speed measurement Doppler radar.

Description

Locomotive speed measurement system and method based on radar near-field echo power spectrum features

technical field

The invention belongs to the technical field of radar near-field measurement, and specifically relates to a locomotive speed measurement method, which is used in complex locomotive electromagnetic environments, different railway subgrade environments, wide radar antenna beams, and errors in antenna beam directions. Under this condition, the measurement of the speed of the locomotive can be realized stably and accurately.

Background technique

At present, in my country's railway system, the measurement of locomotive speed mainly relies on photoelectric sensors. This photoelectric speed measuring device obtains the speed value of the locomotive by measuring the number of revolutions of the locomotive wheels or a rigid shaft. The principle of the photoelectric sensor is simple and easy to implement, but this method of speed measurement will have a certain system deviation when the wheel slips, idling, and the diameter of the wheel changes due to wear, and cannot meet the requirements of high precision and high reliability. In addition, since the maglev train has no wheels, the traditional photoelectric speed measuring equipment cannot measure the speed of the maglev locomotive. Because of this problem, it is a better choice to use radar microwave sensing technology to measure the locomotive speed in a non-contact manner.

Doppler speed measuring radar is one of the applications of radar microwave sensing technology. It uses the Doppler effect generated when microwaves move relative to the roadbed to measure the speed of locomotives. It has the necessary performance against harsh environments. The propagation speed of electromagnetic waves is almost constant in the environment, which makes this method have high accuracy and stability.

The German model DRS05 locomotive speed measuring radar uses the Doppler effect generated when the electromagnetic wave moves relative to the roadbed to measure the speed of the locomotive. Considering that the single-antenna speed measurement is easily affected by the roadbed function, the radar adopts the single-ended dual-antenna structure shown in Figure 1, and uses the beam intersection point K of the dual-antenna as the estimated value of the speed. As shown in Figure 1, under ideal conditions, the intersection point of the spectrum of the two antennas is clear and the position is stable. At this time, no matter whether the maximum value or the intersection point is used to estimate the speed, it is unbiased. But in reality, the spectral curves of the two antennas will change like the shaded part in the figure, and the maximum value of the envelope will move to the left with large fluctuations. At this time, the speed estimated by the maximum value method will be biased. Small. However, from a statistical point of view, it can be considered that the two antenna beams have experienced the same ups and downs of the roadbed function, because when the two antennas sweep the same roadbed function at the same time, the intersection point K of the echo power spectrum of the two antennas will not be like the maximum value Drifting left and right like that, it coincides with the ideal intersection point, as shown in Figure 1. The DRS05 radar measures speed based on the fact that the roadbed function does not affect the position of the intersection point K. The biggest advantage of this technology is that the influence of the roadbed function is eliminated, so the speed measurement accuracy is higher than that of a single antenna. However, due to the difficulty of accurately estimating the intersection point K, although the speed measurement accuracy of the DRS05 radar has been improved, the speed measurement error is still relatively large.

Although theoretically the Doppler speed measuring radar can overcome the shortcomings of the traditional method, is stable and reliable, and can provide accurate measurement accuracy, but in fact, due to factors such as the electromagnetic environment of the locomotive, the geographical environment, the beam width of the radar antenna, and the error of the installation angle of the radar antenna, etc. Influenced by Doppler locomotive speed measuring radar, the accuracy of the locomotive speed measured by the Doppler locomotive speed measuring radar is not high and is easily affected by the installation error of the radar itself. At the same time, it cannot effectively overcome the speed measurement error caused by different roadbed environments.

Contents of the invention

The purpose of the present invention is to overcome the deficiency of above-mentioned Doppler speed measuring radar measuring locomotive speed, has proposed a kind of locomotive speed measurement system and method based on radar near-field echo power spectrum feature, in order to avoid radar speed measuring accuracy being easily affected by locomotive electromagnetic environment, The influence of many factors such as different roadbed environment, beam antenna width and radar antenna installation angle error improves the measurement accuracy.

To achieve the above object, the measurement system of the present invention includes

The sampling rate selection module is used to select the sampling rate to ensure that the relative error of the measured speed value meets the requirements of the locomotive speed measurement, and sends the selected sampling rate data to the pre-estimated speed module of the spectral center of gravity method;

The spectral center of gravity method estimated speed module is used to estimate the locomotive speed corresponding to the center of gravity position of the echo power spectrum of the two antennas of the radar in advance, and sends the estimated speed corresponding to the two antennas to the speed correction module;

The speed correction module is used to correct the estimated speed corresponding to the two antennas, obtain the unbiased estimation of the speed of the locomotive by a single antenna, and send the corrected speeds of the two antennas to the anti-antenna beam angle error module;

The anti-antenna beam angle error module is used to correct the speed measurement error caused by the angle deviation of the two antenna beam centers of the radar, realize the unbiased measurement of the locomotive speed, and obtain the final speed measurement result.

In order to achieve the above object, the measuring method of the present invention is as follows:

(1) Select the sampling rate to be one-tenth of the maximum sampling rate for sampling, and perform FFT operation on the sampling data to obtain the echo power spectrum of the front antenna and the rear antenna respectively;

(2) Use the following formula to calculate the center of gravity in the spectrum region corresponding to the echo power envelope of the front and rear antennas respectively,

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Wherein, E _i is the power amplitude corresponding to the echo power frequency f _i , and f _i is the echo power frequency, which takes values within the minimum and maximum frequency ranges (f _min , f _max );

(3) Multiply the speed corresponding to the center of gravity of the front and rear antennas estimated in step (2) by the correction factor k to obtain the initial unbiased estimation of the locomotive speed using the echo power spectrum of the front and rear antennas respectively. The solution formula of the correction factor is

$\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;E</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula, α is the angle between the beam center direction of the antenna and the horizontal plane, θ _i is the angle between the discretized antenna beam direction and the horizontal plane, and θ _i is within the 3dB beam broadband range of the antenna, that is, within (θ _min , θ _max ) value, E(θ _i ) is the gain of the antenna at the beam angle θ _i ;

(4) Perform secondary correction on the initial unbiased estimated speed of the front antenna by the following formula to obtain the final measurement result of the locomotive speed by the front antenna,

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="d"\; filenames="H2009102192170E00011.png"\; state="\{\{state\}\}">d</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\sqrt{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="tg"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">tg</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Among them, λ is the wavelength of the transmitted wave, α ₁ is the angle between the beam center direction of the front antenna and the horizontal plane, and f _d1 is the frequency corresponding to the initial unbiased estimated speed of the front antenna;

(5) Perform secondary correction on the initial unbiased estimated speed of the rear antenna by the following formula to obtain the final measurement of the locomotive speed by the rear antenna,

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="f\; d"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">f</figure-callout></span><figure-callout\; id="2"\; label="f\; d"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; \&CenterDot;</span>\sqrt{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="tg"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">tg</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Among them, _α2 is the angle between the beam center direction of the rear antenna and the horizontal plane, and f _d2 is the frequency corresponding to the initial unbiased estimated velocity of the rear antenna;

(6) average the final measurement speeds of the front antenna and the rear antenna to obtain the final measurement result of the locomotive speed at the current moment,

$\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="B"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">B</figure-callout></span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ;</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

(7) According to the locomotive speed at the current moment measured in step (6), select the sampling frequency at the next moment according to the relative error of the speed measurement required by the locomotive, and perform FFT calculation on the sampled data to obtain the following values of the front antenna and the rear antenna respectively Echo power spectrum at a moment;

(8) Steps (2) to (7) are cyclically executed to realize real-time measurement of the speed of the locomotive.

Compared with the prior art, the present invention has the following advantages:

(1) The present invention adopts the estimated center of gravity of the echo power envelope as the pre-estimated speed of the locomotive, and uses a correction factor to correct the pre-estimated speed, compared with the speed estimated when the general amplitude maximum method and the correction process are not done more stable and accurate;

(2) The present invention carries out secondary correction and average to the initial unbiased estimated velocity of front and back antennas respectively, has corrected the velocity measurement error that causes by the installation error of antenna or the position offset error that causes in use process, and the velocity that obtains is more accurate stable and accurate;

(3) The present invention selects the sampling frequency of the next moment due to the relative error of speed measurement required by the locomotive, so that the relative error of the measurement speed is basically unchanged. The speed error of the rate measurement;

(4) The measured data shows that the average velocity measurement accuracy of the present invention is less than 0.16%.

The purpose, features and advantages of the present invention can be described in detail by the following drawings and examples.

Description of drawings

Figure 1 is a structure and principle diagram of a German locomotive speed measuring radar model DRS05;

Fig. 2 is a block diagram of the speed measuring system of the present invention;

Fig. 3 is the structural diagram of the locomotive speed measuring radar used in the present invention;

Fig. 4 is a speed measuring process figure of the present invention;

Fig. 5 is the measured curve diagram of locomotive speed estimated by existing maximum method;

Fig. 6 is the actual measurement graph of the locomotive speed that adopts spectrum envelope center of gravity method estimation of the present invention;

Fig. 7 is the actual measurement curve diagram of the locomotive speed measured by the echo data of the front and rear antennas respectively;

Fig. 8 is a curve diagram of actual measurement of locomotive speed after correction of the measurement result of Fig. 7 .

Detailed ways

The content and effects of the present invention will be described in detail below in conjunction with the accompanying drawings.

Referring to Fig. 2, the locomotive speed measurement system includes a module for selecting a sampling rate, a module for estimating speed by spectral center of gravity method, a speed correction module and an anti-antenna beam angle error module.

The sampling rate selection module is used to select the sampling rate to ensure that the relative error of the measured speed value meets the requirements of the locomotive speed measurement, and send the selected sampling rate data to the pre-estimated speed module of the spectral center of gravity method. The frequency resolution of the traditional fast Fourier transform operation is fixed, and the relationship between the speed resolution is determined by the frequency resolution. The speed measurement error obtained by the FFT operation is absolute, that is to say, the relative error is large when the speed of the locomotive is low. However, the relative error is small when the speed is high, which is contrary to the relative speed error required by the locomotive speed measurement system. This module divides the speed of the locomotive into 10 gears from large to small, and each speed corresponds to a sampling frequency. Under the condition that the number of sampling points remains unchanged, find out the speed gear corresponding to the current measured speed value, and select the speed gear for sampling The rate is used as the sampling rate at the next moment to meet the requirements of relative speed measurement accuracy.

The speed estimation module of the spectral center of gravity method is used to predict the locomotive speed corresponding to the center of gravity of the echo power spectrum of the front and rear antennas of the radar, and send the estimated speed corresponding to the front and rear antennas to the speed correction module. The spectrum curve of the echo power of the locomotive speed measuring radar is a fluctuating and asymmetrical envelope affected by the change of the roadbed reflective surface, locomotive vibration and noise factors, directly using the maximum value as the estimated value of the antenna center frequency will have a large error. In order to reduce the error of speed measurement, this module uses the estimated center of gravity of the spectrum to predict the speed of the locomotive, that is, find the spectrum area of the echo power envelope through the relative spectrum width r%, and obtain the center of gravity of the spectrum in this area as the prediction of the speed of the locomotive estimated value. Because the center of gravity of the echo power spectrum curve is low, the pre-estimated value of the center frequency using the spectral center of gravity method is smaller than the true value, which is inaccurate and needs to be corrected in the speed correction module;

The speed correction module is used to correct the pre-estimated speeds corresponding to the two antennas, obtain the initial unbiased estimate of the speed of the locomotive by a single antenna, and send the corrected speeds of the front and rear antennas to the anti-antenna beam angle error module . The spectrum curve of the radar echo power is an asymmetric envelope that deviates from the frequency spectrum corresponding to the real speed, and the center of gravity is too small. The present invention adopts the echo power spectrum feature that the ratio of the locomotive speed estimated by the frequency center of gravity and the real locomotive speed is constant, and the The correction factor is multiplied by the speed estimated by the spectral center of gravity method to obtain the first unbiased estimate of the locomotive speed. Due to the installation angle error of the antenna and the position error caused by the vibration of the locomotive, it will affect the speed measurement accuracy of a single antenna. The speed measurement results of this module need to be corrected twice in the anti-antenna beam angle error module.

The anti-antenna beam angle error module is used to correct the speed measurement error caused by the angle deviation of the front and rear antenna beam centers of the radar, so as to realize the unbiased measurement of the locomotive speed and obtain the final speed measurement. Since the antenna of the Doppler locomotive speed measuring radar always has an installation angle error during installation, the antenna will also have a position error due to random vehicle vibration during the locomotive operation, which leads to the angle between the center direction of the antenna beam and the ground and the real angle There is a certain deviation between them, which causes a certain error in the measurement of the locomotive speed. The present invention utilizes the Doppler radar with dual antennas shown in FIG. 3 to perform secondary corrections on the primary unbiased estimation of the speed of the speed correction module, so as to realize the unbiased measurement of the locomotive speed and obtain the final speed measurement.

With reference to Fig. 4, this locomotive speed measurement method comprises the steps:

Step 1: Select the sampling rate to be one-tenth of the maximum sampling rate for sampling, and perform FFT operation on the sampled data to obtain the echo power spectrum of the front and rear antennas respectively. Since there is no prior information on the speed of the locomotive when the speed of the locomotive is measured for the first time, it is assumed that the locomotive has just started, so the minimum sampling rate of the system is taken as the sampling rate at this moment, that is, one-tenth of the maximum sampling rate is used for sampling.

Step 2, use the following formula to calculate the center of gravity in the spectrum region corresponding to the echo power envelope of the front and rear antennas, respectively,

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; ,</span>$

Among them, E _i is the power amplitude corresponding to the echo power frequency f _i , and f _i is the echo power frequency, which takes values in the minimum and maximum frequency ranges (f _min , f _max ), where the echo power envelope corresponds to The spectral region of is selected with the relative width r% of the spectrum,

$\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; the\; tan</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; sin</span>}\frac{{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="n"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">n</figure-callout></span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}$

In the formula, θ _nn is the 3dB beam width of the antenna, and α is the angle between the center position of the antenna beam and the horizontal plane.

Step 3: Multiply the speed corresponding to the spectral center of gravity of the two antennas estimated in Step 2 by the correction factor k to obtain the initial unbiased estimation of the locomotive speed by the front and rear antennas respectively.

The process of solving the correction factor is as follows:

Set the frequency corresponding to the locomotive speed estimated by the spectral center of gravity as f _b , then

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; v</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; v</span>}$

Among them, v is the real speed of the locomotive, λ is the wavelength of the electromagnetic wave emitted by the antenna, θ _i is the angle between the discretized antenna beam direction and the horizontal plane, E(θ _i ) is the gain of the antenna at the angle θ _i ,

According to the angle α between the antenna beam center position and the horizontal plane and the frequency f _b corresponding to the locomotive speed estimated by the spectrum center of gravity, the ratio of the real speed of the locomotive to the speed measured by the spectrum center of gravity is expressed as:

$\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;E</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}$

The above formula is the correction factor, which is a constant and is also a feature of the echo power spectrum of the Doppler radar antenna for locomotive speed measurement. It shows that using this correction factor to correct the locomotive speed estimated by the center of gravity of the spectrum can obtain a more accurate measurement speed of the locomotive.

Step 5: Perform secondary correction on the initial unbiased estimated speed of the front antenna by the following formula to obtain the final measurement result of the locomotive speed by the front antenna:

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="f\; d"\; filenames="H2009102192170E00011.png"\; state="\{\{state\}\}">f</figure-callout></span><figure-callout\; id="1"\; label="f\; d"\; filenames="H2009102192170E00011.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; \&CenterDot;</span>\sqrt{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="tg"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">tg</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}$

Among them, α ₁ is the angle between the beam center direction of the front antenna and the horizontal plane, and f _d1 is the frequency corresponding to the initial unbiased estimated velocity of the front antenna.

Step 6. Perform secondary correction on the initial unbiased estimated speed of the rear antenna through the following formula to obtain the final measurement of the locomotive speed by the rear antenna:

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="f\; d"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">f</figure-callout></span><figure-callout\; id="2"\; label="f\; d"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\sqrt{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="tg"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">tg</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}$

Among them, α ₂ is the angle between the beam center direction of the rear antenna and the horizontal plane, and f _d2 is the frequency corresponding to the initial unbiased estimated velocity of the rear antenna.

Step 7 averages the final measured speeds of the front antenna and the rear antenna to obtain the final measurement result of the locomotive speed at the current moment:

$\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="v\; B"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">v</figure-callout></span><figure-callout\; id="2"\; label="v\; B"\; filenames="H2009102192170E00021.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; .</span>$

Step 8: According to the locomotive speed at the current moment measured in step 7, select the sampling frequency at the next moment according to the relative error of the speed measurement required by the locomotive, and perform fast Fourier transform operation on the sampled data to obtain the next The echo power spectrum at time.

Step 9 executes step 2 to step 8 in a loop to realize real-time measurement of locomotive speed.

Effect of the present invention can be further illustrated by the following measured data:

Fig. 5 is the measured curve diagram of the locomotive speed estimated by the existing maximum value method, and Fig. 6 is the measured curve diagram of the locomotive speed estimated by the spectrum envelope center of gravity of the present invention, as seen from the comparison of Fig. 5 and Fig. 6, adopting the existing The variance of the locomotive speed estimated by the maximum value method is large and unstable, while the variance of the locomotive speed estimated by the spectrum center of gravity adopted in the present invention is relatively small, stable and has high estimation accuracy.

Fig. 7 is a curve diagram of actual measurement of locomotive speed measured by using the echo data of front antenna and rear antenna respectively, and Fig. 8 is a curve diagram of actual measurement of locomotive speed after the measurement result of Fig. 7 is corrected. It can be seen from Figure 7 that before correction, there is a deviation in the measurement results of the echo data of the front and rear antennas, which is caused by the beam pointing angle error of the front and rear antennas; it can be seen from Figure 8 that after correction, the corresponding measurement speed of the two antennas Together, the correction of the beam angle error is realized, so the estimation of the speed of the locomotive is more stable and more accurate.

In the locomotive speed measurement radar, the measurement error of the locomotive travel distance is used as the measurement accuracy of the locomotive speed measurement radar, as shown in the table.

Table 1 The processing results of the present invention to the sample data of 7 different road sections measured by the front and rear antennas

It can be seen from the data in Table 1 that the method proposed by the present invention is very accurate in measuring the speed of the locomotive, and the maximum measurement error does not exceed 0.16%.

In summary, the present invention fully considers the practical application of the locomotive speed measuring radar, according to the characteristics of the radar near-field echo power spectrum curve, pre-estimates the speed of the locomotive through the center of gravity of the spectrum, and then performs primary correction and secondary correction on the pre-estimated speed. The accurate estimation of the locomotive speed obtained by calibration is not only accurate in speed measurement, but also very robust, and the actual operation is in good condition.

Claims (4)

1. A locomotive speed measurement system based on radar near-field echo power spectrum features, comprising: The sampling rate selection module is used to select the sampling rate to ensure that the relative error of the measured speed value meets the requirements of the locomotive speed measurement, and sends the selected sampling rate data to the pre-estimated speed module of the spectral center of gravity method; The spectral center of gravity method estimated speed module is used to estimate the locomotive speed corresponding to the center of gravity position of the echo power spectrum of the two antennas of the radar in advance, and sends the estimated speed corresponding to the front and rear antennas to the speed correction module; The speed correction module is used to correct the estimated speed corresponding to the front and rear antennas, obtain the initial unbiased estimate of the speed of the locomotive by a single antenna, and send the corrected speeds of the two antennas to the anti-antenna beam angle error module; The anti-antenna beam angle error module is used to correct the speed measurement error caused by the angle deviation of the front and rear antenna beam centers of the radar, realize the unbiased measurement of the locomotive speed, and obtain the final speed measurement result. 2. A method for measuring the speed of a locomotive based on radar near-field echo power spectrum features, comprising the following processes: (1) Select the sampling rate to be one-tenth of the maximum sampling rate for sampling, and perform FFT operation on the sampling data to obtain the echo power spectrum of the front antenna and the rear antenna respectively; (2) Use the following formula to calculate the center of gravity in the spectrum region corresponding to the echo power envelope of the front and rear antennas respectively, ${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$ Wherein, E _i is the power amplitude corresponding to the echo power frequency f _i , and f _i is the echo power frequency, which takes values within the minimum and maximum frequency ranges (f _min , f _max ); (3) Multiply the speed corresponding to the center of gravity of the front and rear antenna echo power spectra estimated in step (2) by the correction factor k to obtain the initial unbiased estimation of the locomotive speed using the echo power spectra of the front and rear antennas respectively, and the solution of the correction factor The formula is $\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;E</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$ In the formula, α is the angle between the beam center direction of the antenna and the horizontal plane, θ _i is the angle between the discretized antenna beam direction and the horizontal plane, and θ _i is within the 3dB beam broadband range of the antenna, that is, within (θ _min , θ _max ) value, E(θ _i ) is the gain of the antenna at the beam angle θ _i ; (4) Perform secondary correction on the initial unbiased estimated speed of the front antenna by the following formula to obtain the final measurement result of the locomotive speed using the front antenna, ${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\sqrt{{\mathrm{<span\; class="notranslate">\; tg</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$ Among them, λ is the wavelength of the transmitted wave , α ₁ is the angle between the beam center direction of the front antenna and the horizontal plane, and f _d1 is the frequency corresponding to the initial unbiased estimated speed of the front antenna; (5) Perform a secondary correction on the initial unbiased estimated speed of the rear antenna by the following formula to obtain the final measurement of the locomotive speed using the rear antenna, ${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\sqrt{{\mathrm{<span\; class="notranslate">\; tg</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$ Among them, _α2 is the angle between the beam center direction of the rear antenna and the horizontal plane, and f _d2 is the frequency corresponding to the initial unbiased estimated velocity of the rear antenna; (6) average the final measurement speeds corresponding to the front and rear antennas to obtain the final measurement results of the locomotive speed at the current moment; $\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$ (7) According to the locomotive speed at the current moment measured in step (6), select the sampling frequency at the next moment according to the relative error of the speed measurement required by the locomotive, and perform FFT calculation on the sampled data to obtain the front antenna and the rear antenna respectively in the next Echo power spectrum at time; (8) Steps (2) to (7) are cyclically executed to realize real-time measurement of the speed of the locomotive. 3. the locomotive speed measuring method according to claim 2 is characterized in that the spectrum region described in the step (2) is to select with the relative width r% of the spectrum, $\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; the\; tan</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; sin</span>}\frac{{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; n</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$ In the formula, θ _nn is the 3dB beam width of the antenna, and α is the angle between the center position of the antenna beam and the horizontal plane. 4. the locomotive speed measurement method according to claim 2, is characterized in that the sampling rate of the selection next moment described in the step (7) is that the locomotive speed is divided into 10 gears according to from large to small, each gear speed Corresponding to a sampling frequency, under the condition that the number of sampling points remains unchanged, find out the speed gear corresponding to the current measured speed value, and select the sampling rate of this speed gear as the sampling rate at the next moment.

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